A senior Russian military officer has said Russia has a special forces unit in Syria carrying out reconnaissance and "other special tasks."

"I will not hide the fact that on the territory of Syria there is a division of our special operations forces," Interfax quoted Aleksandr Dvornikov, a commander of the Russian contingent in Syria, as saying on March 23.

President Vladimir Putin last week ordered a pullout of some Russian warplanes from Syria, but said that strikes against the Islamic State (IS) group and the Al-Qaeda-linked Al-Nusra Front will continue.

"They perform supplementary reconnaissance on targets for Russian air strikes, they are engaged in guiding aircraft to targets in remote areas and perform other special tasks."

His comments come amid reports Syrian government forces and their allies have advanced within 1 kilometer of Palmyra.

IS militants seized Palmyra in May 2015.

Analysts say the recapture of the desert city would be one of the most prominent successes for President Bashar al-Assad since Russia launched a military intervention in September that turned the tide of Syria's civil war in his favor.

Palmyra is the site of ancient Roman-era temples and colonnades, many of them destroyed by the militants.